In the conventional keeled hull, as was formerly known, heeling was controlled by a ballasted keel which extended fore and aft of the hull and below the same along the centerline or midplane. The keel was normally laterally fixed in position at the midplane so that the angle of heel could be changed only by lateral motion of ballast (sandbags) or lateral motion of crew weight. The keelless hull concept evolved to overcome the above limitations and disadvantages of previous yacht designs.
In the keelless hull shown in U.S. Pat. No. 5,163,377, issued Nov. 17, 1992 to Calderon et al. and entitled SAILING YACHT, a dynamic, laterally swingable or canting ballast is suspended generally beneath the hull to provide a counter heeling force when the yacht is underway. While providing significant improvements over fixed keel designs in respect to heeling resistance and roll stability, it has been observed that in some conditions it would be desirable to augment the counter heeling effect achieved with dynamic ballast. For instance, when the ballast is positioned at a limit position thereof and fluctuations in operating conditions are experienced, such as when an increase in true wind velocity above high true wind average is experienced, additional counter heeling force is not available from the dynamic ballast and the vessel may assume an undesired angle of heel.
Another instance is when the designer chooses to decrease lead weight of ballast to enhance downwind performance, in which case canting a higher weight is not possible, even though additional righting movements are desirable.
The magnitude of control force normally required to position the ballast can limit responsiveness of the strut and impact the yacht's ability to compensate for turbulent operating conditions, such as choppy water or shifting winds. Further, the ballast weight necessary to achieve an appropriate righting moment in all circumstances can contribute adversely to the vessel's overall weight and consequently effect the vessel's ability to achieve and maintain a hydroplaning condition of the hull. The need exists for an improved design wherein all of the above factors are considered and addressed.